Method and apparatus for aligning workpieces

ABSTRACT

Disclosed here are methods and automatic apparatus for grinding cylindrical workpieces, such as the contoured rolls used in metal rolling mills. The methods and apparatus involve (1) automatic finding of the lengthwise center of rolls of different and undetermined lengths so as to establish a reference position for the execution of a numerically programmed path defined relative to the center of a roll as a point of symmetry, (2) the storage of the successive instructions of multi-axis movements making up a numerically defined profile or contoured path, and the use of those instructions repeatedly and in whole or in part as called for by different ones of a sequence of commands read from storage and executed in succession, (3) the automatic alignment of the roll axis parallel to the longitudinal axis of motion in a grinding machine by pivoting of one end of the roll about the other until the sensed difference in positions of the roll surface, along an axis transverse to the longitudinal axis and at locations near opposite ends of the roll, is changed to a predetermined fraction of the originally sensed difference, (4) the initiation of grinding passes from that end of a roll which is largest in diameter, so as to avoid &#39;&#39;&#39;&#39;digging in&#39;&#39;&#39;&#39; or increasing the depth of wheel bite as the wheel moves lengthwise of the roll, (5) the execution of continuous passes of the grinding wheel with pre-programmed values of feed rate, wheel speed, roll speed, continuous infeed and incremental infeed until a pre-programmed thickness of material has been removed from the roll surface, and (6) the grinding down of a roll until it is reduced to a diameter equal that of a previously ground roll of a matched pair. These functions are all obtained by the calling out and execution of pre-established routines in response to the reading from storage of pre-programmed sequence commands, so that in the disclosed method and apparatus there is an automatic progression from each type of operation to the next, and with the following of numerically defined profile whenever it is required.

limited States Patent Clarlgjr.

[54] METHOD AND APPARATUS FOR ALIGNING WORKPIECES Stephen C. Clark, Jr., Phoenixville, Pa.

The Ingersoll Milling Machine Company, Rockford, Ill.

[22] Filed: Jan. 25, 1971 [21] Appl. No.: 109,524

Related US. Application Data [62] Division of Ser. No. 790,323, Jan. 10, 1969.

[ 72] Inventor:

[73] Assignee:

s2 u.s.c|. ..5l/l65'I'P,51/49,51/289R 51 Int. Cl ..B24b 5/04 58 FieldofSearch ..5l/49,165R,165TP,165.71,

5l/l65.74, 165.75, 165.76, 165.77, 289 R, 326, 327; 82/14 B, 14 D, 21 B Primary Examiner--Lester M. Swingle Att0rney-Wolfe, Hubbard, Leydig, Voit & Osann [5 7] ABSTRACT Disclosed here are methods and automatic apparatus for [451 May 23, 1972 grinding cylindrical workpieces, such as the contoured rolls used in metal rolling mills. The methods and apparatus involve (l) automatic finding of the lengthwise center of rolls of different and undetermined lengths so as to establish a reference position for the execution of a numerically programmed path defined relative to the center of a roll as a point of symmetry, (2) the storage of the successive instructions of multi-axis movements making up a numerically defined profile or contoured path, and the use of those instructions repeatedly and in whole or in part as called for by different ones of a sequence of commands read from storage and executed in succession, (3) the automatic alignment of the roll axis parallel to the longitudinal axis of motion in a grinding machine by pivoting of one end of the roll about the other until the sensed difference in positions of the roll surface, along an axis transverse to the longitudinal axis and at locations near opposite ends of the roll, is changed to a predetermined fraction of the originally sensed difference, (4) the initiation of grinding passes from that end of a roll which is largest in diameter, so as to avoid digging in or increasing the depth of wheel bite as the wheel moves lengthwise of the roll, (5) the execution of continuous passes of the grinding wheel with pre-programmed values of feed rate, wheel speed, roll speed, continuous infeed and incremental infeed until a pre-programmed thickness of material has been removed from the roll surface, and (6) the grinding down of a roll until it is reduced to a diameter equal that of a previously ground roll of a matched pair. These functions are all obtained by the calling out and execution of preestablished routines in response to the reading from storage of pre-programmed sequence commands, so that in the disclosed method and apparatus there is an automatic progression from each type of operation to the next, and with the following of numerically defined profile whenever it is required.

10 Claims, 27 Drawing Figures Patented May 23, 1972 6 3,664,066

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METHOD AND APPARATUS FOR ALIGNING WORKPIECES TAB LE OF CONTENTS Column Abstract ofthe Disclosure Fl. Cross-Reference to a Related Application Background ofthe Invention...

Summary ofthe Invention 2 Brief Description ofthe Drawings 3 Description of Preferred Embodiments 3 A. An Exemplary Machine Tool 3 B. Control Instrumentalities on the Grinding Machine 6 1. Feedback Pulse Generators 6 2. SteadyrestServomotor 6 3. Sensing Switches 7 4. Probe Assemblies 7 5. Proximity Switches 9 C. The ControlSystem in General 9 l. Contouring Apparatus l 2. Sequence Command System l2 3. Data Manipulation Apparatus 13 D. Methods and Apparatus for GrindingaRoll 15 1. Setup Procedure 15 2. Location of Lengthwise Center; M61 17 (a) Movement of the Swivel Base to the Center ofB Axis Travel 17 (b) Setting the Platform 35 to the Center of X Axis Travel 18 (c) Movement of Proximity Switches to Operative Positions 18 (d) Movement ofWheel to CenterofRoll l9 3. Automatic Alignment ofthe Roll Axis 23 (a) Startup Operations 24 (b) Movement to Location of First Gaging Band 25 (c) Bringing the Wheel into Touching Contact with the Roll 26 (d) Grinding Right Gage Band to Predetermined Depth 27 (e) Movement of Wheel to Location of Left Gage Band 28 (f) Grinding of the Left Gaging Band 29 (8) R e traction of the Wheel Free of the Roll... 2 (h) Sensing the Location of the Left Gaging Band on the Rear Side of the Roll.. 30 4. Determining Direction of First Grinding Pass; Initial Grinding 35 (a) Right End Larger 37 (b) Left End Larger 38 (c) Status of the System Prior to First Grind-- ing Pass 38 (d) First Grinding Pass and Continuous Passing 39 (i) Case I Material Removal Incomplete 40 (ii) Case ll Material Removal Complete 41 5. Rough Grinding 42 6. Finish Grinding 43 7. Sensing and Signaling the Roll Diameter 44 8. Cleaning Up the Roll Surface by Sparking Passes 49 9. Polishing Passes 50 E. Grinding aSecond Roll to the Same Diameter 52 F. An Alternative Embodiment 56 CROSS-REFERENCE TO A RELATED APPLICATION This application is a division of my copending application, Ser. No. 790,323, filed Jan. 10, 1969.

BACKGROUND OF THE INVENTION The present invention relates in general to methods and apparatus for the turning of cylindrical workpieces, and while it will find advantageous use in the operation of lathes, the invention is adapted to be applied with special advantages in the operation of grinding machines for shaping or renewing the shape of rolls such as those employed in metal rolling mills.

In the operation of large installations for the rolling of steel or aluminum into thin sheets or strips for coiling, the high inter-roll pressures and roll speeds result in severe wear of the surfaces of the individual rolls. The wear is often non-uniform, and any roll surface irregularities result in magnified surface imperfections in the sheets or strips. It is common practice to change the rolls in a given mill stand frequently, as often as once per 8-hour shift. When each worn roll is removed from the mill, there is a need to have its surface re-finished or reground to nearly perfect smoothness and with the desired cylindrical shape (which may be a convex or concave contour lengthwise of the roll to compensate for roll loading pressure and produce a desired cross sectional shape in the rolled strip).

To grind any roll to a given contour, the roll must be supported by the grinding machine with the axis of the roll disposed parallel to the longitudinal path of travel followed by the grinding wheel as the latter moves lengthwise along the roll. Unless the roll axis is made parallel with the longitudinal path, the roll will be formed with an imprecise shape after grinding has been completed.

In most cases, uneven wear on the roll journals or necks makes it practically impossible for even skilled machinists to place the roll initially in the grinding machine in a position such that the axis of the roll is aligned parallel with the longitudinal path followed by the grinding wheel. Accordingly, it is the usual practice to place the roll in the machine in an approximately aligned position, to detect the degree of misalignment and thereafter to shift or adjust the roll as necessary to eliminate the misalignment and thus position the roll axis parallel to the longitudinal path of the grinding wheel.

SUMMARY OF THE INVENTION The principal objective of the present invention is to provide a new and advantageous method and apparatus for aligning the axis of a cylindrical workpiece parallel with the path of longitudinal movement of a tool in a turning machine. More specifically, it is an object of the invention to use a sensor to detect the degree of misalignment of one end of a cylindrical workpiece, to adjust such one end in a direction transverse to the longitudinal motion of a tool and, by utilizing the same sensor which initially detects misalignment, to sense and signal when the necessary corrective adjustment has been completed.

The invention thus is characterized by the provision of novel apparatus which needs only a single workpiece surface sensor to detect the degree of misalignment of a workpiece and to control shifting of the workpiece to a properly aligned position.

Another object is to obtain quickly and preferably automatically the complete operation of sensing misalignment of a workpiece axis and adjusting the workpiece in a turning machine to align the workpiece axis, irrespective of whether the workpiece is initially cylindrical or tapered, i.e., has equal or unequal diameters at its opposite ends.

A further object of the invention is to reduce the time consumed in conditioning the workpiece preparatory to detecting its misalignment with the workpiece surface sensor and, in particular, this is achieved by forming comparatively short gaging bands near the ends of the workpiece and by utilizing the gaging bands as the detecting surfaces for the sensor.

The foregoing summary of the invention and the advantageous objectives achieved thereby will be better understood after consideration of the more detailed description of a specific, exemplary embodiment of the methods and ap- 

1. The method of aligning the longitudinal axis of a nominally cylindrical workpiece parallel to the path of a tool in a turning machine; said machine having left and right journaling supports for receiving the opposite ends of the workpiece, a tool carriage movable along a straight-line Z axis generally parallel to the surface of a workpiece journaled on said supports, means for moving the tool toward and away from the workpiece relative to the carriage along an X axis transverse to the Z axis, and means for moving the right support to different positions in a direction substantially parallel to the X axis; said method comprising the steps of placing the workpiece in or on said supports; bringing the tool to a first position along the Z axis and feeding it inwardly from a reference point to a first X axis position to cut a gaging band on the workpiece, bringing the tool to a second position along the Z axis and feeding it inwardly to the same X axis position to cut a second gage band on the workpiece, said second Z axis position being spaced a distance G along the Z axis to the left of the first Z axis position and being spaced a distance A to the right of the left support, measuring and signaling the initial difference ( Delta ) between the initial displacements of the first and second gage band surfaces at points on such surfaces diametrically opposite to the points of contact by the tool during cutting of such surfaces to a reference line parallel to the Z axis and lying in the diametrical plane defined by said points, moving the right support in a direction corresponding to the sign of said initial difference ( Delta ) while continuing to signal the changing difference as the workpiece is pivoted about a point located at the left support, and terminating the movement of the right steadyrest when the changing diffErence signal represents a value equal to Delta (G - A)/2G .
 2. The method set forth in claim 1 further including the steps of moving the tool along the Z axis while retracted from the workpiece to that end of the workpiece closest to (a) said first gage band or (b) said second gage band in response to said difference signal having (a) one polarity or (b) the other polarity, respectively, bringing the tool inwardly along the X axis to cut a predetermined small increment into the workpiece, and moving the tool along the Z axis toward the opposite end of the workpiece to execute a first cutting pass with the tool bite becoming progressively smaller.
 2. means to produce an electrical signal (E) indicative of the sense and magnitude of the probe displacement, and thus of distance of the workpiece surface from a reference position; and e. means for adjustably positioning said right support in a direction substantially parallel to the X axis; said method comprising the steps of a. placing the workpiece in or on said journaling supports; b. cutting left and right gaging bands on the workpiece; separated along the Z axis by a predetermined distance G and with the left band separated from the left journaling support by a distance A, by bringing the tool into cutting engagement with the workpiece and to the same absolute position along the X axis, so that tool contact elements on the surfaces of the two bands lie on a line parallel to the Z axis, c. extending the probe into engagement with the surface of the left gage band and setting the electrical signal (E) from the probe assembly to zero; d. thereafter extending the probe into engagement with the surface of the right gage band and storing the initial electrical signal (Eo) produced by the probe assembly; e. producing a second electrical signal E'' equal to (G - A)/2G times the stored initial signal (Eo), f. and moving the right journaling support in a direction corresponding to the sense of the electrical signal (E) produced by the probe assembly and until the latter signal becomes equal to said second electrical signal (E'').
 3. The method of aligning the axis of a roll parallel to the path of a grinding wheel extending generally lengthwise of the roll in a grinder, said grinder having right and left steadyrests for journaled support of the two necks of the roll, a grinding wheel carrier movable along a straight-line Z axis which extends generally lengthwise of a journaled roll, means supporting said wheel on the carrier for movement along an X axis transverse to the Z axis, and means for adjusting said right steadyrest to different positions along a line substantially parallel to said X axis, said method comprising the steps of placing the roll with its necks journaled in the steadyrests and rotationally driving the roll, bringing the wheel to a first Z axis position and feeding it inwardly from a reference point to first X axis position to grind a first gage band on the roll, bringing the wheel to a second Z axis position and feeding it inwardly to said first X axis position to grind a second gage band on the roll, sensing the initial displacement of said second gage band surface, at a point diametrically opposite the point of wheel contact during grinding of such surface, from a reference line parallel to the Z axis, sensing the initial displacement of said first gage band surface, at a point diametrically opposite the point of contact during grinding of such surface, from said reference line, signaling the initial difference ( Delta ) between said initial displacements, and moving said right steadyrest while continuing to sense the displacement of said first gage band surface until the difference between it and said initial displacement of the second gage band surface becomes equal to a target value (e), said target value being equal to the said initial difference ( Delta ) multiplied by a fraction whose numerator is the difference (G-A) between the distance (G) lengthwise of the roll between said gage bands and the distance (A) between said left gage band and the left steadyrest, and whose denominator (2G) is twice the distance (G) between said gage bands.
 4. The method of aligning the longitudinal axis of a nominally cylindrical workpiece parallel to the path of a tool in a turning machine; said machine having a. left and right journaling supports for receiving the opposite ends of the workpiece, b. a tool movable along a straight line Z axis generally parallel to the surface of a workpiece journaled in said supports and movable toward and away from the workpiece along an X axis which is transverse to the Z axis, c. means for adjustably positioning said right support along a line substantially parallel to said X axis, and d. a probe assembly movable along the Z axis and having a probe engageable with the surface of the workpiece along a line which is diametrically opposite on the workpiece from the line of contact between the tool and the workpiece when the latter is being cut with Z axis movement of the tool, said method comprising the steps of, a. placing the workpiece in or on said supports, b. bringing the tool to a first Z axis position and moving the tool along the X axis to a predetermined X position relative to an X axis reference, thereby to cut a right gage band on the workpiece, c. Bringing the tool to a second Z axis position spaced leftward of the first by a distance G and moving the tool along the X axis to said predetermined position to cut a left gage band on the workpiece, the left and right gage band surfaces at locations contacted by the tool lying on a line parallel to the Z axis, d. bringing the probe assembly to a Z axis position opposite said left gage band, extending the probe into engagement with the left gage band surface, and signaling the distance (P1) which the probe extends from probe assembly. e. bringing the probe assembly to a Z axis position opposite said right gage band, extending the probe into engagement with the band surface, and signaling the difference ( Delta ) between the distance (P2) which the probe extends from the probe assembly and the distance (P1) which it extended during said step (d), f. utilizing the signaled difference ( Delta ) to compute and signal the value of the quantity Delta (G - A)/2G, g. moving the right steadyrest in a direction corresponding to the sign of the difference ( Delta ) determined during said step (d) while continuing the engagement of the probe with said right gage band surface and the signaling of the changing difference between the changing distance (P2) which the probe extends from the probe assembly and the distance (P1) which it extended during said step (d), and stopping the steadyrest when the signaled changing difference equals said signaled quantity Delta (G - A)/2G.
 5. The method of aligning a nominally cylindrical but tapered workpiece so that its longitudinal axis and axis of rotation will be parallel to the path of longitudinal travel in a turning machine tool, said machine tool having a. left and right journaling supports for receiving the opposite ends of the workpiece, b. a tool carriage movable along a straight line Z axis generally longitudinally of the supported workpiece, c. a tool movable with the carriage and also movable relative thereto along an X axis which is transverse to the Z axis, d. a probe assembly supported on the carriage and movable therewith along the Z axis, said assembly being located on that side of the workpiece diametrically opposite the tool and having
 6. In a control system for a turning machine adapted to receive a cylinDrical workpiece in left and right journaling supports, said machine having a tool movable along a linear Z axis which may or may not be parallel to the workpiece axis after the latter is first placed in the machine, the combination comprising means for producing and storing a first signal (Eo) which in magnitude represents the initial difference between (a) the spacing between a reference line parallel to the Z axis and the workpiece surface at first axial location, and (b) the spacing between said reference line and the workpiece surface at a second axial location spaced by a distance G to the left of the first location and by a distance A to the right of the left journaling support, means energized by said first signal for producing a target signal (E'') equal to the first signal multiplied by the fraction (G - A)/2G, means for producing a changeable signal (E) which varies in proportion to the aforesaid difference, and means responsive to said target signal and said changeable signal for moving said right journaling support in a direction normal to said Z axis until the changeable signal becomes equal to said target signal, thereby to bring the axis of the workpiece substantially into parallelism with the Z axis.
 7. The combination set forth in claim 6 further including a motor for driving said right journaling support in a direction normal to said Z axis, means for producing a control signal proportional to the difference (E - E'') between said changeable signal and said target signal, and means for energizing said motor with said control signal.
 8. For use with a grinding machine having left and right journaling supports adapted to receive the left and right ends of a nominally cylindrical roll, a tool movable along a linear Z axis generally parallel to the longitudinal axis of the workpiece and movable along an X axis substantially normal to the Z axis, the right support being adjustable parallel to the X axis in a horizontal plane, the combination comprising means for producing a changeable signal (E) which varies in proportion to the difference between (a) the spacing between a reference line parallel to the Z axis and the roll surface at a first axial location and (b) the spacing between said reference line and the roll surface at a second axial location spaced by a distance G to the left of the first location and by a distance A to the right of the left journaling support, said reference line, and roll surface locations lying in a horizontal plane which embraces a wheel contact element of the roll, means responsive to said changeable signal for producing an unchanging signal Eo equal to the initial value of said changeable signal for a given roll placed in the machine, means responsive to said unchanging signal for producing a target signal (E'') equal to the unchanging signal multiplied by the fraction (G - A)/2G, and means for driving said right journaling support parallel to the X axis until the changeable signal becomes equal to the target signal.
 9. The combination set forth in claim 8, wherein said means for producing said changeable signal (E) includes a probe assembly movable along the Z axis and having a probe body movable parallel to the X axis, a probe extensible relative to the body to a position determined by its contact with the roll surface, and means for producing a voltage signal proportional to the displacement of the probe from a reference position relative to the body; control means for adjusting said body to make said voltage signal zero when said probe is engaged with the roll at said second axial location; and control means for then moving said probe into engagement with the roll surface at said first axial location without changing the position of said body in a direction parallel to the Z axis, whereupon said voltage signal constitutes said changeable signal proportional to said spacing difference.
 10. The combination set forth in claim 8 further including means for subtractively combining said changeable signal and said target signal to create a control signal proportional to their difference (E - E''), and means responsive to said control signal for moving said right journaling support to swing the roll axis in a horizontal plane about the left journaling support until the control signal is reduced to zero. 